In modern digital transmission systems facsimile calls are transmitted in the same channel as voice and voiceband data calls. Recently, facsimile, voice and voiceband data calls have been transmitted in the same channel by employing voiceband signal compression techniques such as Adaptive Differential PCM (ADPCM) and digital speech interpolation. Additionally, it is noted that no indication is provided, by associated switching or other equipment, to the transmission network as to the nature of the current call, i.e., facsimile, voice or voiceband data.
The increase in use of facsimile has led to the inefficient utilization of prior transmission resources. This inefficiency results because traditional analog or modem based facsimile transmission is time and bandwidth intensive. This reduces the effectiveness of prior signal compression techniques and, consequently, the other signals, e.g., voice and voiceband data, cannot share the channel bandwidth resources.